Closed What is Dkms in linux? how it works?

[-cynika_]

DKMS (Dynamic Kernel Module Support) package (You do not have permission to view the full content of this post. Log in or register now.) provides support for installing supplementary versions of kernel modules. The package compiles and installs into the kernel tree. Uninstalling restores the previous modules. By default, installation is into the current kernel tree, but any kernel tree can be selected with command-line options. Furthermore, DKMS is called automatically upon installation of new Ubuntu kernel-image packages, and therefore modules added to DKMS will be automatically carried across updates.

Overview

To use a module with DKMS, one places the module installation files (could be source code or binary) in /usr/src/-, along with a configuration file dkms.conf that tells DKMS how to build/configure the module and what its name is. Under more advanced scenarios, conditional build instructions and patching can be done by the dkms system, but considering on your case this may not be necessary.

Walk-through

Let's say you want to install a module for your fancy "Awesome Adaptor." You are given a source tarball awesome-20091211-v1.1.tgz.

With DKMS, we tell DKMS how to do that for you by creating a dkms.conf file with the appropriate entries. For example, after we've unpacked the tarball:

# cd awesome-20091211-v1.1/
# touch dkms.conf
# create dkms.conf file
# vi dkms.conf

Inside dkms.conf, we might add the lines:

MAKE="make -C src/ KERNELDIR=/lib/modules/${kernelver}/build"
CLEAN="make -C src/ clean"
BUILT_MODULE_NAME=awesome
BUILT_MODULE_LOCATION=src/
PACKAGE_NAME=awesome
PACKAGE_VERSION=1.1
REMAKE_INITRD=yes

All directories are with respect to the location of the dkms.conf file. This tells DKMS

1. The command to build the module (run make in the directory src/).
2. The command to clean the source tree (run make clean in the directory src/).
3. The name of the module without the .o or .ko extension. This may actually be an array of modules if multiple modules are built, see man dkms.
4. Where DKMS can find the built module.
5. The name and version DKMS should associate with the module(s).
6. To remake the initrd image after installing the module.

You can also add options to call scripts before or after build or install, provide additional (conditional) make commands, ρá†ch commands, etc. The dkms.conf is in fact sourced into a shell script, so a fair amount of trickery can be done if necessary. These options and more are described in the dkms.conf section in man dkms.

Next, we install the module into DKMS by copying the module installation files into the kernel source tree /usr/src/- and tell DKMS about the new module:

# ls
README dkms.conf lib src
# sudo cp -R . /usr/src/awesome-1.1
# sudo dkms add -m awesome -v 1.1
dkms does its thing...

That's it! DKMS has now added our module to its list of modules to build for future kernel installations. To make sure it works and to install the module into our current kernel, we can instruct dkms to build and install the module:

# sudo dkms build -m awesome -v 1.1
dkms does its thing.... watch for build errors... you may need to tweak dkms.conf
# sudo dkms install -m awesome -v 1.1
dkms does its thing.... module is copied into current kernel module tree